Evolution of porewater in a Neogene sedimentary formation in the Horonobe area, Hokkaido, Japan: Modeling of burial diagenesis

Miyakawa, Kazuya; Kashiwaya, Koki*; Komura, Yuto*; Nakata, Kotaro*

Geochemical Journal, 57(5), p.155 - 175, 2023/00

https://doi.org/10.2343/geochemj.GJ23014

In the thick marine sediments, groundwater altered from seawater during the burial diagenesis may exist. Such altered ancient seawater will be called fossil seawater. In such a field, groundwater flow is considered extremely slow because it is not affected by the seepage of meteoric water even after the uplift. During diagenesis, dehydration from silicates causes changes such as a decrease in the salinity of the porewater. However, dehydration reactions alone cannot quantitatively explain water chemistry changes. In this study, we developed an analytical model that considers the dehydration reaction from silicates during the burial process and the upward migration of porewater due to compaction and examined the possible evolution of porewater chemistry. The results showed that the water chemistry, which was strongly influenced by the dehydration reaction from opal-A to quartz and from smectite, was similar to the observations from boring surveys. The results suggest that the fossil seawater formed during the diagenesis may have been preserved since the uplift and strongly supports the slow groundwater flow in the area where the fossil seawater exists.

Characteristics in trace elements compositions of tephras (B-Tm and To-a) for identification tools

Nara, Fumiko*; Yokoyama, Tatsunori; Yamasaki, Shinichi*; Minami, Masayo*; Asahara, Yoshihiro*; Watanabe, Takahiro; Yamada, Kazuyoshi*; Tsuchiya, Noriyoshi*; Yasuda, Yoshinori*

Geochemical Journal, 55(3), p.117 - 133, 2021/00

https://doi.org/10.2343/geochemj.2.0619

The absolute date of the Millennium Eruption (ME) of Changbaishan Volcano is widely recognized as AD 946. The Baegdosan-Tomakomai (B-Tm) tephra dispersed during the ME is a robust-age key bed. In order to identify the tephra, refractive index and major-element compositions of volcanic glass shards are conventionally used. However, trace-element analysis has been rarely carried out, especially for rare-earth elements (REEs) and for tephra layer bulk sediments. Here we present the datasets of major- and trace-element compositions datasets for the glass shards and bulk sediments of the B-Tm and Towada caldera eruptions (To-a) tephra deposits from the Lake Ogawara sediment core, Tohoku region, northern Japan. The depth profiles of the major and trace elements show the significant peaks for the KO and some trace elements (Zn, Rb, Zr, Nb, Sn, Y, La, Ce, Nd, Th, and U) at the B-Tm tephra layer in the Lake Ogawara sediment core, but no peaks of these elements at the To-a tephra layer. High concentrations of the trace elements in the B-Tm tephra layer were observed in individual glass shards as well as in the bulk sediment. These concentrations are highlighted by the elemental abundance pattern normalized by the crustal abundance. The elemental pattern in individual glass shards from other Japanese tephras showed significant differences from those of the B-Tm tephra, especially in REEs compositions. The trace-element compositions of the glass shards and bulk sediment show strong advantages for distinguishing the B-Tm tephra from other Japanese tephras.

Application of M-edge XANES to determination of U oxidation state in zircon

Tanaka, Kazuya; Takahashi, Yoshio*

Geochemical Journal, 53(5), p.329 - 331, 2019/00

https://doi.org/10.2343/geochemj.2.0568

We examined three natural zircon samples with different amounts of radiation doses using M-edge and L-edge U X-ray absorption near-edge structure (XANES). Analysis of XANES spectra at both M-edge and L-edge suggested that the oxidation state of U in the zircon sample with the highest radiation dose is tetravalent. The XANES spectra of the two other samples with lower radiation doses suggested a mixture of U(IV) and U(VI), while the possibility of U(V) was not excluded. This is the first work on the application of M-edge U XANES to the oxidation state of U in natural zircon.

Characterization of mineralogical controls on ammonium concentrations in deep groundwaters of the Horonobe area, Hokkaido

Sasamoto, Hiroshi; Sato, Hisao*; Arthur, R. C.*

Journal of Geochemical Exploration, 188, p.318 - 325, 2018/05

https://doi.org/10.1016/j.gexplo.2018.01.013

Ammonium is potentially an important constituent of deep groundwater under reducing condition. The retention of cesium by sorption in geological formations may have an important role ensuring the long-term safety of high-level radioactive waste. Cesium sorption will be affected by competing effects due to dissolve cation likely ammonium in groundwater, however. In the present study, a possible reaction to control of ammonium in deep groundwater was evaluated based on the data selected in the Horonobe as a test case in Japan. Results of investigation of mineralogy, thermodynamic evaluation of groundwaters and the Electron Probe Micro Analysis (EPMA) to identify nitrogen distribution on minerals suggest that the clay minerals bearing potassium, particularly smectite, illite and interstratified illite/smectite, appear to control the ammonium concentration in groundwaters by ion exchange reactions. Additionally, the selected groundwaters in the Horonobe seem to resemble to the gas and oil fields groundwater in the screened dataset in Japan in terms of ammonium distribution.

Analysis of two forms of radioactive particles emitted during the early stages of the Fukushima Dai-ichi Nuclear Power Station accident

Satou, Yukihiko; Sueki, Keisuke*; Sasa, Kimikazu*; Yoshikawa, Hideki; Nakama, Shigeo; Minowa, Haruka*; Abe, Yoshinari*; Nakai, Izumi*; Ono, Takahiro*; Adachi, Koji*; et al.

Geochemical Journal, 52(2), p.137 - 143, 2018/00

https://doi.org/10.2343/geochemj.2.0514

Discovery of ion-adsorption type deposits of rare earth elements (REE) in Southwest Japan with speciation of REE by extended X-ray absorption fine structure spectroscopy

Yamaguchi, Akiko*; Honda, Tasuku*; Tanaka, Masato*; Tanaka, Kazuya; Takahashi, Yoshio*

Geochemical Journal, 52(5), p.415 - 425, 2018/00

https://doi.org/10.2343/geochemj.2.0531

Ion-adsorption type REE deposits in weathered granite are main sources of REE essential for high-technology industries. However, these type deposits have not been searched in Japan. In this study, Bulk REE abundances (= REE), ion-exchangeable REE (= REE) by ammonium chloride solution, and percentage of REE relative to REE (= REE) in fresh and weathered granite samples in Southwest Japan (i.e., Hiroshima and Shimane Prefectures) were determined. The REE and REE were comparable to those of ion-adsorption type REE deposits in China. Extended X-ray adsorption fine structure (EXAFS) spectra of REE in original samples and samples after the extraction of ion-exchangeable REE showed that (i) REE in samples with high REE mainly forms outer-sphere complexes and (ii) the remaining REE in the rocks after the extraction forms inter-sphere complexes.

Factors controlling Cs activity concentrations in sediment collected off the coast of Fukushima Prefecture in 2013-2015

Fukuda, Miho*; Aono, Tatsuo*; Yamazaki, Shinnosuke*; Ishimaru, Takashi*; Kanda, Jota*; Nishikawa, Jun*; Otosaka, Shigeyoshi

Geochemical Journal, 52(2), p.201 - 209, 2018/00

https://doi.org/10.2343/geochemj.2.0504

To elucidate recent activity levels and the behavior of radiocesium in the coast off Fukushima Prefecture, lateral and vertical distributions of Cs in sediment were observed in 2013-2015 at 12 monitoring stations. At stations around the water depth of 100 m, relatively higher Cs activities were observed from surface sedimentary layer (0-3 cm). In these stations, sediments had high content of silt to clay particles and organic matter. The high Cs activities in the surface sediments were attributed to accumulation of highly mobile sediment particles. In October 2014, at some coastal stations, sharp peaks of Cs activities were observed in the subsurface (5-16 cm) sediments, whereas such broad peaks were not found in October 2015. These results suggest that the Cs activities in sediment had largely changed by lateral transport and re-sedimentation on the surface, as well as sediment mixing in the middle-layers.

Iridium concentration and noble gas composition of Cretaceous-Tertiary boundary clay from Stevns Klint, Denmark

Osawa, Takahito; Hatsukawa, Yuichi; Nagao, Keisuke*; Koizumi, Mitsuo; Oshima, Masumi; Toh, Yosuke; Kimura, Atsushi; Furutaka, Kazuyoshi

Geochemical Journal, 43(6), p.415 - 422, 2009/00

https://doi.org/10.2343/geochemj.1.0038

The Cretaceous-Tertiary (K-T) boundary about 65 million years ago records a mass extinction event caused by a bolide impact. K-T boundary clay collected from Stevns Klint, Denmark was investigated in this work. Iridium concentrations of eight clays across the K-T boundary were determined using a multiple -ray analysis system after neutron activation. Anomalously high Ir concentrations were detected in five marl samples, with the highest concentration being 29.9 ppb. Four samples were analyzed for all noble gases. No extraterrestrial Ar, Kr, and Xe were discovered in any of the samples, although most of the He which was detected was extraterrestrial. Solar-like Ne was observed only in the sample SK4, which had an Ir concentration of 14.3 ppb, indicating the presence of micrometeorites.

Natural attenuation of antimony in mine drainage water

Manaka, Mitsuo*; Yanase, Nobuyuki; Sato, Tsutomu*; Fukushi, Keisuke*

Geochemical Journal, 41(1), p.17 - 27, 2007/00

https://doi.org/10.2343/geochemj.41.17

Natural attenuation was investigated for the antimony in the drainage water of an abandoned mine. Drainage water, waste rocks, and ocherous precipitates collected from the mine were investigated in terms of their mineralogy and chemistry. The chemistry of the drainage water was analyzed by measuring pH, ORP, and EC on site as well as by ICP-MS and ion chromatography. The results of these investigations indicated that Sb, which is generated by the dissolution of stibnite (SbS) and secondary formed Sb minerals in waste rocks, was attenuated by iron-bearing ocherous precipitates, especially schwertmannite, that form over time in the drainage water. Bulk distribution coefficients (Kd) for this Sb adsorption to the precipitates ranges up to at least 10 L/kg.

Geostatistical and Geochemical Classification of Groundwaters Considered in Safety Assessment of a Deep Geologic Repository for High-Level Radioactive Wastes in Japan

Yui, Mikazu; Sasamoto, Hiroshi; Arthur, R. C,*

Geochemical Journal, 38(1), p.33 - 42, 2004/00

https://doi.org/10.2343/geochemj.38.33

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